Surgical head clamps or skull clamps generally are provided with two types of mechanisms to hold the head in position. The first type of clamps use pads that are forced against the patient's head to hold the head in position. Examples of head clamps of type are disclosed in U.S. Pat. Nos. 4,108,426 and 4,545,572.
The second type of head clamps use a series of head engaging pins which engage the patient's skull at three points and provide positive anchorage of the head engaging pins into the skull. If the head engaging pins are held in a stable held in position, there is little likelihood that the skull will move relative to the head engaging pins during the surgical procedure.
The head clamp disclosed in U.S. Pat. No. 2,966,383 shows a three pin arrangement with the head engaging pins carried on hinged arms.
U.S. Pat. No. 3,099,441 discloses a surgical head clamp which contains two head engaging pins on a bracket supported by an arm and a third head engaging pin supported by another arm in the device. The two arms are brought together to adjust the space between the head engaging pins to fit the dimensions of the patient's head.
U.S. Pat. No. 3,835,861 discloses a surgical head clamp having three head engaging pins with two of the pins on a bracket and a third pin on a moveable pin carrier in which one of the pins is held on a threaded pin carrier so finer adjustments in the relationship of the head engaging pins to the patient can be made.
U.S. Pat. No. 4,169,478 also discloses a surgical head clamp with three head engaging pins which is similar to that shown in U.S. Pat. No. 3,835,861. The head clamp includes a mechanism to rotate the bracket containing the two pins and reposition the head of the patient without releasing the head engaging pins from the patient's skull. The mechanism employed to allow the rotation includes a number of ball actuators that are received in sockets. The rotation of an operating handle displaces the balls and allows the bracket to be rotated to permit the turning of the head without releasing the pin members from the head.
Although the surgical head clamp disclosed in U.S. Pat. No. 4,169,478 does offer certain advantages to the physicians, the problem exists in that the bracket can be inadvertently turned which may cause the head to move in the bracket and could cause injury to the patient. The weight of the patient in certain operating positions could exert a force against the bracket which might cause the bracket to turn if the ball actuators are not firmly seated in the sockets of the actuator disk.